The sleeves are not a must-have, as mentioned above. If you're not comfortable installing the seals over the lock grooves directly, cut a small piece of a sandwich baggie to drape over the stem & groove locks, and put some oil on the "cover" to let the seal slide right over.

If you need to remove them after installation and don't want to risk tearing the seal lip, wrap the lock groove with Scotch tape and gently twist the seal over the taped area while pulling the seal up the stem. That's a derivation of an old trick to keep from tearing up the front suspension ("fork") seals on dirt bikes if you need to disassemble them for internal tuning changes or maintenance.